Harpo is the stage name of Adolph Arthur Marx — the silent, harp-playing member of the Marx Brothers whose physical comedy and complete refusal to speak on screen made him one of Hollywood's most distinctive comedic presences. On a male dog, it's a name for an owner who loves classic film and appreciates a quiet, expressive animal.
The Marx Brothers Connection
The Marx Brothers — Groucho, Harpo, Chico, and Zeppo — defined American comedy in the 1930s. Harpo, who never spoke in any film, communicated entirely through physical gesture, honking a horn, and playing the harp with astonishing skill. A dog named Harpo inherits both the silence implication (dogs can't talk either) and the gentle absurdity of naming an animal after someone defined by not speaking.
The Classic Cinema Owner Type
Harpo is a dog name for a specific kind of owner: someone who watches Turner Classic Movies, knows the difference between Duck Soup and A Night at the Opera, and finds naming a dog after a 1930s comedian to be exactly the right kind of obscure. Compare Groucho, which occasionally appears in the same registry tier.
The Counter-Reading: Obscurity as Feature
Most people at the dog park won't catch the reference. Whether that's a drawback or the entire point depends on the owner. For owners who want a name that rewards the informed observer, Harpo delivers perfectly.